As a type of a three-dimensional image recognition unit using glasses, an anaglyph type, a passive type, an active type, and the like are known. In the anaglyph type, display quality is exceptionally poor bad and so-called crosstalk occurs. Both the passive and active types use polarized glasses.
In the passive type, while the polarized glasses can be manufactured lightweight at low cost, in order to generate a left-eye image and a right-eye image, it is necessary to separately provide right-eye and left-eye pixels. Since three-dimensional image display requires a spatial resolution twice that of normal two-dimensional image display, in general, the resolution of a three-dimensional image is low. The display quality is low compared to the active type. It is also necessary to pattern and form a polarizing element, such as a λ/2 plate, for each pixel, resulting in an increase in cost of an image display device.
The active type has excellent display performance. For example, when the spatial resolution of an image display device (hereinafter, referred to as a 3D display device) for a three-dimensional image recognition unit is full high-definition (1920×1080), stereoscopic display can be performed with the resolution of full high-definition. The primary performance which is required for a 3D display device of an active type is high frame rate and high-performance image processing capability, and these can be satisfied in an existing high-end image display device. That is, the image display device can be developed as a 3D display device before the widespread use of 3D content without providing a special member in the image display device itself.
Hereinafter, polarized glasses which are used in the active type are referred to as active shutter glasses. As the active type of three-dimensional image recognition unit, for example, a technique using liquid crystal shutter lens-type active shutter glasses, which have a pair of polarizing plates and a liquid crystal layer interposed between the pair of polarizing plates is disclosed (for example, see Patent Literature 1).